/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicInteger;

import com.google.common.annotations.GwtCompatible;

/**
 * Multiset implementation backed by an {@link EnumMap}.
 * 
 * @author Jared Levy
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible
public final class EnumMultiset<E extends Enum<E>> extends
        AbstractMapBasedMultiset<E> {
    /** Creates an empty {@code EnumMultiset}. */
    public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) {
        return new EnumMultiset<E>(type);
    }

    /**
     * Creates a new {@code EnumMultiset} containing the specified elements.
     * 
     * @param elements
     *            the elements that the multiset should contain
     * @throws IllegalArgumentException
     *             if {@code elements} is empty
     */
    public static <E extends Enum<E>> EnumMultiset<E> create(
            Iterable<E> elements) {
        Iterator<E> iterator = elements.iterator();
        checkArgument(iterator.hasNext(),
                "EnumMultiset constructor passed empty Iterable");
        EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next()
                .getDeclaringClass());
        Iterables.addAll(multiset, elements);
        return multiset;
    }

    private transient Class<E> type;

    /** Creates an empty {@code EnumMultiset}. */
    private EnumMultiset(Class<E> type) {
        super(new EnumMap<E, AtomicInteger>(type));
        this.type = type;
    }

    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(type);
        Serialization.writeMultiset(this, stream);
    }

    /**
     * @serialData the {@code Class<E>} for the enum type, the number of
     *             distinct elements, the first element, its count, the second
     *             element, its count, and so on
     */
    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        @SuppressWarnings("unchecked")
        // reading data stored by writeObject
        Class<E> localType = (Class<E>) stream.readObject();
        type = localType;
        setBackingMap(new EnumMap<E, AtomicInteger>(type));
        Serialization.populateMultiset(this, stream);
    }

    private static final long serialVersionUID = 0;
}
